[알고리즘문제풀기] 세로 읽기

문제

내가 작성한 정답

String

class Solution {
    public String solution(String my_string, int m, int c) {
        String answer = "";
        for(int i=0; i<my_string.length(); i+=m){
            answer += String.valueOf(my_string.charAt(c-1+i));
        }
        return answer;
    }
}

StringBuilder, StringBuffer

class Solution {
    public String solution(String my_string, int m, int c) {
        StringBuilder answer = new StringBuilder();
        // StringBuffer answer = new StringBuffer();
        for(int i=0; i<my_string.length(); i+=m){
            answer.append(String.valueOf(my_string.charAt(c-1+i)));
        }
        return answer.toString();
    }
}

2차 배열

class Solution {
    public String solution(String my_string, int m, int c) {
		    //StringBuilder answer = new StringBuilder();
		    //StringBuffer answer = new StringBuffer();
        String answer = "";
        int len = my_string.length(), le = len%m==0?len/m:len/m+1, idx = 0;
        String[][] ms = new String[le][m];
        for(int i=0; i<le; i++){
            for(int j=0; j<m; j++){
                ms[i][j] = String.valueOf(my_string.charAt(idx++));
            }
        }
        for(int i=0; i<le; i++){
		        //answer.append(ms[i][c-1]);
            answer += ms[i][c-1];
        }
        //return answer.toString();
        return answer;
    }
}

Stream

import java.util.stream.*;

class Solution {
    public String solution(String my_string, int m, int c) {
        return IntStream.range(0,my_string.length()%m==0?my_string.length()/m:my_string.length()/m+1)
                .mapToObj(i-> my_string.substring(i*m,(i+1)*m))
                .map(s->String.valueOf(s.charAt(c-1)))
                .collect(Collectors.joining());
    }
}

다른 사람들의 정답

import java.util.stream.*;

class Solution {
    public String solution(String myString, int m, int c) {
        return IntStream.range(0, myString.length())
            .filter(i -> i % m == c - 1)
            .mapToObj(i -> String.valueOf(myString.charAt(i)))
            .collect(Collectors.joining());
    }
}